The present invention relates to a method and system for analyzing overhead-line arrangements with radar.
Overhead-line arrangements such as used for electrical transmission or distribution lines include two principal components: the lines themselves, which may include conductors and/or static lines, and a mechanism for supporting the lines overhead. In some instances, the supporting mechanism uses spaced wooden poles. The power-utility-system infrastructure alone in North America includes approximately 150,000,000 wooden pole structures used to support overhead lines. A similarly large number of wooden poles are additionally used by the telecommunications industry. There are a numerous aspects of this infrastructure that are required to conform with various specifications and which are subject to periodic assessment for compliance with those specifications.
For example, while wood remains valuable as a material for constructing power and telecommunications poles because of its cost effectiveness and reasonable durability, they are, nevertheless, subject to deterioration over time. This deterioration arises not only from climatic effects, but also from biological and mechanical assaults. Biological deterioration may result from the activity of decay fungi, wood-boring insects, or birds. Woodpeckers have been known to bore vertical tunnels in wooden poles greater than twelve feet in length. Mechanical damage can result from such things as vehicular collisions or shotgun impacts. Consequently, each wooden pole in the system must be inspected periodically and a determination made whether to replace the pole based on the strength of the pole. Typically, poles are inspected on a 5-9 year cycle.
Various methods currently exist for evaluating pole strength, generally requiring direct physical contact with the pole. Such methods rely primarily on sampling techniques in which the strength of the pole is deduced from an assessment of its characteristics at the sampled points. Such sampling is typically performed in the region of the pole easily accessible by a technician, i.e. between about six feet above the ground to about two feet below the ground, so that only about 10% of the pole is even within the sampling region. Crossarms, which are positioned near the tops of the poles, are rarely examined for deterioration. Current methods also tend to include significant reliance on the qualitative assessment of the technician examining the pole. Individual visits to every pole to perform the inspection additionally result in substantial costs for maintaining the pole infrastructures.
In addition to the functional integrity of the utility pole being dependent on the structural soundness of the wooden pole and crossarm structures, it may also depend on the condition of other insulative pole structures. For example, many utility poles are equipped with “insulators,” which are knobs that are affixed to the poles, usually on the crossarms, and are used to support the utility lines. The insulators may be fabricated of appropriate insulative material, such as rubber, fiberglass, ceramic, or porcelain. The insulators are also exposed to weather and biological deterioration that may adversely affect their performance. In some cases, cracks may form in the insulators and later be filled with water or metal. The change in electrical character may result in flashover, which may trip circuitry and in some cases cause a fire that burns the wooden crossarm, or causes even greater damage.
Furthermore, a number of aspects of how the infrastructure may be used depend specifically on the geometry of the overhead lines. For example, one parameter that is particularly relevant when the overhead lines comprise bare overhead conductor lines is the line sag, which corresponds to the minimum separation between the overhead line and the ground surface. If the distance between the line and the ground is too small, there is a danger of having a change of phase to ground, i.e. of producing arcing between the conductor line and the ground. A determination of an acceptable geometry, including the distance between the ground and the line, depends on a number of factors, including environmental factors such as temperature and operational factors such as the load to be carried by the line. Moreover, the line sag may potentially differ throughout the infrastructure depending on how the lines were hung and environmental factors, among other factors.
There is accordingly a need in the art for improved methods and systems for analyzing overhead-line arrangements, including the ability to evaluate the integrity of insulative structures and to define the geometry of the overhead-line arrangement.